The present invention relates generally to pipelines containing pressurized fluid, and more particularly to a junction for connecting adjacent pipes in a pipeline such that the pipeline is capable of accommodating accumulated thermal expansion in the pipes.
Pipelines carrying pressurized fluid over long distances are known for a variety of applications. For example, vehicle systems have been proposed which comprise an elongated tubular guideway for storing and delivering pressurized fluid, typically air, to a vehicle for levitating and/or propelling the vehicle along the guideway. One such system is described, for example, in commonly owned U.S. patent application Ser. No. 08/912,245 filed Aug. 15, 1997, now U.S. Pat. No. 5,909,710. In such systems, the guideway itself is a twin tube pipeline made up of a plurality of pipes each having a pair of sealing bulkheads located at opposite ends thereof. The tube segments are joined end-to-end to define the guideway, which may include lateral supports for the vehicles or serve as a direct support or track for the vehicles. In many vehicle systems of the type thus far described, the pipes are elevated above ground by a series of supports spaced along the guideway.
A recognized problem, particularly in locations where wide variations in outdoor temperature are known to occur, is that of thermal expansion and contraction of the pipes forming the guideway or pipeline. The pipes must be supported and connected in a manner that allows for significant longitudinal (axial) thermal expansion while maintaining accurate guidance of the vehicles traveling therealong. This must be done while maintaining a pressure seal throughout the length of the pipeline/guideway, and allowing a continuous flow passage for filling and pressure recovery over the length of the pipeline/guideway. The axial thrust generated in the pipes by internal pressure should either be safely constrained or neutralized, and the stiffness and load carrying ability of the pipes should be compromised as infrequently as possible by joints and interconnections.
The present invention comprises a junction for joining a first section with an adjacent second section in a guideway carrying pressurized fluid. The junction comprises female end portions on a first section, male end portions on a second section partially received within the female end portions, and a vessel. The vessel comprises a plenum bounded at one end by a piston. The plenum is in flow communication with a pressure source.
Therefore, it is an object of the present invention to provide a pipeline junction for a single or twin tube guideway that compensates for pressure changes in the fluid and length changes in the pipeline.